History Flags
History Flags — control the behavior of a history.
Description
These flags are returned by
the flags parameter of the describe
command. The flags associated with a history control key
aspects of its behaviour. Each constant is a mask for the
individual flag bits, and can be used to test the returned
parameter. Separate commands are used to set the flags.
The flags are summarized as follows:
- HIST_DISABLED
- Controls whether new values for the
point associated with the history are logged. Set to
1 by the disable
command, cleared (to 0) by the
enable
command. The default state is 0
(active).
- HIST_REGISTERED
- Controls whether the point
associated with the history is registered with the
Cascade DataHub. If the point is registered, then all
changes to the value in the datahub will be sent to
the Cascade Historian. This flag is set by the register
command, and cleared by the unregister
command. The default state is 0
(unregistered).
- HIST_DEADBAND
- Controls whether a deadband is in
use. A deadband is a range relative to the current
value of the history within which value changes will
be ignored. This is used to avoid storing values
that represent just 'noise'. If no deadband is in
effect, or the deadband value is
0, then all value updates are
stored. A deadband can be expressed as an absolute
value or as a percent. This flag is set or cleared
by the deadband
command. The default state is 0
(no deadband).
- HIST_DEADBAND_PERCENT
- When this flag bit is set the value
of the deadband (if in use) is treated as a percent
of the current history value. This flag is set or
cleared by the deadband
command. The default value is 0
(absolute deadband value).
Example
if (((flags & HIST_DISABLED) != HIST_DISABLED) &&
((flags & HIST_REGISTERED) == HIST_REGISTERED))
{
item.active = 1;
}
